TWI661601B - Electrode forming material for lithium secondary battery and production method for electrode - Google Patents

Abstract

An object of the present invention is to provide an active material coated on an electrode of a current collector with high density and close contact with the current collector when the electrode active material and the conductive auxiliary agent are coated on the current collector with an adhesive. An adhesive having excellent properties, and an electrode forming material including the adhesive, and a method for forming an electrode using the electrode forming material.

The means for solving the problem is an electrode forming material, which is an electrode forming material coated on a current collector. The electrode forming material includes an electrode active material and a binder. The binder includes a carboxyl group-containing polysaccharide and a carboxyl group. The reaction product of polysaccharides and epoxy compounds, or a combination thereof, has a viscosity in the range of 20 to 1500 mPa · s at 25 ° C in a 3% by mass aqueous solution of the adhesive. The carboxyl group-containing polysaccharide system is preferably carboxymethyl cellulose, alginic acid, or a salt thereof. As the electrode active material, lithium-cobalt composite oxide or graphite can be used. As the conductive aid, a carbon raw material can be used.

Description

Electrode forming material for lithium battery and manufacturing method of electrode

The present invention relates to an electrode forming material and a method for manufacturing an electrode using the electrode forming material, and particularly to an electrode forming material for a lithium battery and a method for manufacturing an electrode for a lithium battery.

As a power source for home appliances or automobiles, lithium batteries have been widely used in recent years. In particular, lithium batteries with high battery voltage and high energy density have attracted much attention as power sources.

The electrodes used in conventional lithium batteries are usually formed by coating and covering an electrode forming material (slurry) containing an electrode active material, a binder (binding agent), and the like on a current collector, and then firing the electrode. .

For example, as the binder component, carboxymethyl cellulose or a salt thereof and a mixture with fluororubber have been proposed. Examples of the fluorine rubber include a copolymer of tetrafluoroethylene and difluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, and polytrifluorochloroethylene (see Patent Document 1).

Also, it is disclosed that a Li complex oxide is used as an active material and a ring-containing compound is used. A compound of oxirane ring and / or the polymer is used as a component for improving the flexibility of an electrode or for improving the adhesion with an active material, and further, carboxymethyl cellulose or a salt thereof is used as the component Electrode for tackifier battery. As the aforementioned ethylene oxide ring-containing compound, polyoxyethylene diglycidyl ether is disclosed (see Patent Document 2).

Furthermore, an electrode for a lithium secondary battery is disclosed, which is characterized by having an electrode composite material layer including an electrode active material and a binding material covering the surface of the electrode active material, the binding material containing cellulose Derivatives are hydrophilic binding materials, and electrophilic electrolyte binding materials containing a polyether structure in the chemical structure (see Patent Document 3).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 5-101829

[Patent Document 2] Japanese Patent Laid-Open No. 8-069789

[Patent Document 3] Japanese Patent Laid-Open No. 2003-249225

In a lithium secondary battery, an electrode active material existing on a current collector is charged and discharged by exchange of lithium ions and serves as a central substance of the battery. A material for increasing the moving speed of electrons of the electrode active material is a conductive additive. As mentioned above, the electrode system is usually an electrode forming material (slurry) that contains an electrode active material, a conductive auxiliary agent, and a binder. This is applied to a current collector, followed by drying, pressing, etc., that is, it is formed by using a binder and coating the current collector with an electrode active material and a conductive auxiliary agent.

At this time, the density of the electrode active material in the electrode (that is, in the layer covering the current collector) is increased as much as possible, and the adhesion between the electrode forming material (that is, the coating layer) and the current collector is as follows: It is excellent in terms of battery reliability (lifetime, safety, etc.) and battery performance (capacity retention rate, etc.), so it is required to satisfy these electrode materials.

The object of the present invention is to provide an electrode active material and an electrically conductive auxiliary agent which are coated on a current collector with an adhesive to form an electrode. The electrode active material in the electrode will have a high density and be formed by the electrode active material. An electrode forming material having excellent adhesion between the covering layer and the current collector is provided, and a method for forming an electrode using the electrode forming material is also provided.

As a result of in-depth research to solve the above-mentioned problems, the inventor found that when a specific adhesive having a specific viscosity is used as a component of the electrode forming material, and the electrode forming material is used to cover the current collector to form the electrode, The density of the electrode active material is higher than in the past, and the adhesion between the coating layer and the current collector made of the electrode forming material is excellent, and the present invention has been completed.

The first aspect of the invention of the present application is an electrode forming material, which is an electrode forming material coated on a current collector. The electrode forming material includes an electrode active material and a binder. The binder includes Carboxyl polysaccharides, reaction products of carboxyl-containing polysaccharides and epoxy compounds, or a combination of these, in a 3% by mass aqueous solution of the adhesive at 20 ° C to 1500mPa‧s at 25 ° C The viscosity of the range.

A second aspect is the electrode forming material according to the first aspect, wherein the carboxyl group-containing polysaccharide is at least one selected from the group consisting of carboxymethyl cellulose, alginic acid, and salts thereof.

A third aspect is the electrode forming material according to the first aspect or the second aspect, wherein the epoxy compound is an epoxy compound represented by the formula (1): (In the formula (1), X represents a hydrogen atom, a mono or poly (oxyalkylene) group having 1 to 30 repeating units, an n-valent aliphatic hydrocarbon group having 1 to 30 carbon atoms that can be substituted, An aryl group having 6 to 30 carbon atoms, or a combination thereof, wherein n is an integer of 1 to 10).

The fourth aspect is the electrode forming material according to any one of the first aspect to the third aspect, and further includes a conductive auxiliary agent.

A fifth aspect is the electrode forming material according to any one of the first to fourth aspects, wherein the electrode active material is a lithium-cobalt composite oxide or graphite.

A sixth aspect is the electrode forming material according to the fourth aspect, wherein the conductive auxiliary agent is made of a carbon material.

A seventh aspect is an electrode manufacturing method, which includes the steps of mixing the electrode forming material of any one of the first to sixth aspects with water to produce a slurry of the electrode forming material, and The slurry of the electrode forming material is applied to a current collector, and is heated at a temperature of 80 to 160 ° C. to form a film of the electrode forming material, and a step of pressing the aforementioned film from above the film.

As described above, when an electrode-forming material containing an electrode active material, preferably a conductive additive, and a binder is used to cover the current collector and form the electrode, the electrode active material in the electrode becomes high-density, and Covering the body with excellent adhesion is preferable from the viewpoint of battery performance and the like.

In the case of using carboxymethyl cellulose, which has been widely used as an electrode-forming material as a binder, when this is applied to a current collector, uneven coating may occur, and the surface of the current collector may be partially exposed. This is considered to be because the viscosity of the binder (carboxymethyl cellulose) is high, so the solid content concentration of the slurry of the electrode forming material is reduced, and the density of the electrode active material and the conductive auxiliary agent in the formed electrode is reduced. reason.

In the present invention, the viscosity of carboxymethyl cellulose is preferably adjusted by modifying the carboxymethyl cellulose to improve the applicability of the slurry of the electrode forming material to the application of the current collector. Get the so-called electrode The electrode active material has a higher density than the past, and the adhesion between the coating layer and the current collector made of the electrode forming material is improved.

In more detail, by using epoxy resin to modify carboxymethyl cellulose, the molecular weight as an adhesive is increased, and at the same time, the viscosity of the adhesive itself is reduced.

In this way, the present invention achieves an increase in the molecular weight and a decrease in viscosity of the adhesive itself, which can increase the content of the electrode active material and the conductive auxiliary agent in the slurry of the electrode forming material. As a result, the so-called The effect of coating unevenness on the surface of the current collector is reduced, and more electrode active materials and conductive additives can be present on the surface of the current collector. In addition, by increasing the molecular weight of the adhesive, the adhesiveness of the adhesive to the current collector can be improved, that is, the adhesiveness of the electrode active material and the conductive auxiliary agent to the current collector can be improved, and It is also possible to obtain an effect that the charge-discharge characteristics of a battery using the electrode are improved.

As described above, the present invention is to form an electrode forming material that sets the viscosity of a binder that affects coating performance within a specific range, and an electrode manufactured by using the slurry of the electrode forming material can obtain so-called good charge and discharge. Effect of characteristics.

[Fig. 1] Fig. 1 is an electron microscope photograph showing the applicability of the slurry of the electrode forming material obtained in Example 1 to a current collector. The left half of the photo shows the part photographed at 500x magnification, and the right half is a table The part photographed at a magnification of 1000 times is shown.

[Fig. 2] Fig. 2 is an electron microscope photograph showing the applicability of the slurry of the electrode forming material obtained in Example 2 to a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 3] Fig. 3 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Example 3 on a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 4] Fig. 4 is an electron microscope photograph showing the coating property of the slurry of the electrode-forming material obtained in Example 4 on the current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 5] Fig. 5 is an electron microscope photograph showing the applicability of the slurry of the electrode forming material obtained in Example 5 to a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[FIG. 6] FIG. 6 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Example 6 on the current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 7] Fig. 7 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Example 7 on the current collector. The left half of the photo shows the part photographed at 500x magnification, and the right half is a table The part photographed at a magnification of 1000 times is shown.

[FIG. 8] FIG. 8 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Example 8 on the current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[FIG. 9] FIG. 9 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Example 9 on the current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 10] Fig. 10 is an electron microscope photograph showing the coating property on the current collector of the slurry of the electrode forming material obtained in Comparative Example 1. [Fig. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[FIG. 11] FIG. 11 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Comparative Example 2 on a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 12] Fig. 12 is an electron microscope photograph showing the coating property on the current collector of the slurry of the electrode forming material obtained in Comparative Example 3. [Fig. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 13] Fig. 13 is an electron microscope photograph showing the coating property of the slurry of the electrode forming material obtained in Comparative Example 4 on a current collector. The left half of the picture shows the part photographed at 500 times magnification, and the right half is Shows the part photographed at 1000 times magnification.

[Fig. 14] Fig. 14 is an electron microscope photograph showing the coating property of the slurry of the electrode-forming material obtained in Comparative Example 5 on a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[FIG. 15] FIG. 15 is an electron microscope photograph showing the coating property of the slurry of the electrode-forming material obtained in Comparative Example 6 on a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 16] Fig. 16 is a photograph in which the slurry of the electrode forming material obtained in Example 1 and Comparative Example 5 was applied to a current collector, and the presence or absence of peeling of the electrode was shown.

[Fig. 17] Fig. 17 is an electron microscope photograph showing the applicability of the slurry of the electrode-forming material obtained in Example 10 to a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 18] Fig. 18 is an electron microscope photograph showing the coating property of the slurry of the electrode-forming material obtained in Example 11 on the current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Fig. 19] Fig. 19 is an electron microscope photograph showing the applicability of the slurry of the electrode-forming material obtained in Example 12 to a current collector. The left half of the photograph indicates the part photographed at 500 times magnification, and the right half of the photograph indicates the part photographed at 1000 times magnification.

[Best Mode for Implementing Invention]

The present invention relates to an electrode forming material, which is an electrode forming material coated on a current collector. The electrode forming material includes an electrode active material and a binder. The binder includes a carboxyl group-containing polysaccharide and a carboxyl group. The reaction product of a saccharide and an epoxy compound, or a combination thereof, has a viscosity in a range of 20 to 1500 mPa · s at 25 ° C in a 3% by mass aqueous solution of the adhesive.

In the electrode forming material of the present invention, the binder may be a carboxyl group-containing polysaccharide, a reaction product of a carboxyl group-containing polysaccharide and an epoxy compound, or a combination thereof.

When the carboxyl group-containing polysaccharides and the reaction product of carboxyl group-containing polysaccharides and epoxy compounds are used in combination, that is, when a mixture of polysaccharides and reaction products is used, (carboxyl group-containing polysaccharides): ( A reaction product of a carboxyl group-containing polysaccharide and an epoxy compound) is used in a range of 1: 100 to 100: 1 or 1:10 to 10: 1 by mass.

The carboxyl group-containing polysaccharide is a saccharide formed by polymerizing a plurality of monosaccharide molecules by glycoside bonding and having a carboxyl group in a unit structure.

Examples of such carboxyl group-containing polysaccharides include alginic acid, xanthan gum, pectinic acid, carboxy cellulose, and the like, and examples of the aforementioned salts include ammonium, sodium, and potassium salts.

Among them, carboxymethyl-containing polysaccharides are preferably carboxymethyl cellulose, which is a part to all of the hydrogen atoms of a hydroxyl group in a structure of cellulose, or a hydrogen atom of an oxygen atom bonded to a hydroxymethyl group. A cellulose derivative having a structure partially or entirely substituted with carboxymethyl (-CH ₂ COOH).

The degree of substitution of carboxymethyl cellulose (degree of etherification per unit of anhydrous glucose (maximum 3)) used in the present invention can be used in the range of 0.5 to 1.5.

In the present invention, the modified epoxy compound used for the carboxyl group-containing polysaccharide is preferably an epoxy compound having a structure represented by the formula (1).

In the aforementioned formula (1), the X-based hydrogen atom, the number of repeating units is 1 to 30 or a poly (oxyalkylene) group, and the n-valent aliphatic hydrocarbon group having 1 to 30 carbon atoms can be substituted. An aryl group having 6 to 30 atoms or a combination thereof, and n is an integer of 1 to 10.

The above-mentioned n-valent aliphatic hydrocarbon group means a group obtained by removing n hydrogen atoms bonded to a carbon atom from an alkane, and examples thereof include an alkyl group and an alkylene group (alkanediyl group). , Alkane triyl, alkane tetrayl, alkane pentayl, alkane hexayl, alkane heptyl, alkane octyl, alkane nonyl, or alkane decayl.

Examples of the alkyl group, that is, an alkyl group having 1 to 30 carbon atoms include methyl, ethyl, n-propyl, i-propyl, cyclopropyl, n-butyl, i-butyl, and s -Butyl, t-butyl, cyclobutyl, 1-methyl-cyclopropyl, 2-methyl-cyclopropyl, n-pentyl, 1-methyl-n-butyl, 2-methyl -n-butyl, 3-methyl-n-butyl, 1,1-dimethyl-n-propyl, 1,2-dimethyl-n-propyl, 2,2-dimethyl- n-propyl, 1-ethyl-n-propyl, cyclopentyl, 1-methyl-cyclobutyl, 2-methyl-cyclobutyl, 3-methyl-cyclobutyl, 1,2-dimethyl-cyclopropyl, 2,3-dimethyl-cyclopropyl, 1-ethyl-cyclopropyl , 2-ethyl-cyclopropyl, n-hexyl, 1-methyl-n-pentyl, 2-methyl-n-pentyl, 3-methyl-n-pentyl, 4-methyl-n -Pentyl, 1,1-dimethyl-n-butyl, 1,2-dimethyl-n-butyl, 1,3-dimethyl-n-butyl, 2,2-dimethyl -n-butyl, 2,3-dimethyl-n-butyl, 3,3-dimethyl-n-butyl, 1-ethyl-n-butyl, 2-ethyl-n-butyl Group, 1,1,2-trimethyl-n-propyl, 1,2,2-trimethyl-n-propyl, 1-ethyl-1-methyl-n-propyl, 1-ethyl 2-methyl-n-propyl, cyclohexyl, 1-methyl-cyclopentyl, 2-methyl-cyclopentyl, 3-methyl-cyclopentyl, 1-ethyl-cyclobutyl , 2-ethyl-cyclobutyl, 3-ethyl-cyclobutyl, 1,2-dimethyl-cyclobutyl, 1,3-dimethyl-cyclobutyl, 2,2-dimethyl -Cyclobutyl, 2,3-dimethyl-cyclobutyl, 2,4-dimethyl-cyclobutyl, 3,3-dimethyl-cyclobutyl, 1-n-propyl-cyclopropane Group, 2-n-propyl-cyclopropyl, 1-i-propyl-cyclopropyl, 2-i-propyl-cyclopropyl, 1,2,2-trimethyl-cyclopropyl, 1 , 2,3-trimethyl-cyclopropyl, 2,2,3-trimethyl-cyclopropyl, 1 -Ethyl-2-methyl-cyclopropyl, 2-ethyl-1-methyl-cyclopropyl, 2-ethyl-2-methyl-cyclopropyl, and 2-ethyl-3-methyl -Cyclopropyl and the like.

The alkylene group, that is, an alkylene group having 1 to 30 carbon atoms, may be, for example, an alkylene group corresponding to the alkyl group (after removing one hydrogen atom bonded to a carbon atom from the alkyl group) The resulting base).

Moreover, as another n-valent aliphatic hydrocarbon group having 1 to 30 carbon atoms, for example, a group obtained by removing a plurality of arbitrary hydrogen atoms bonded to a carbon atom from the alkyl group (specifically 3 to 3) 30).

Moreover, aliphatic hydrocarbon groups such as the above-mentioned alkyl group and alkylene group Examples of the replaceable functional group include a hydroxyl group, an amino group, a cyano group, an acrylfluorenyl group, a methacrylfluorenyl group, a mercapto group, an epoxy group, a glycidyl group, an epoxypropyloxy group, and a halogen group ( A fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkoxy group, and the like. These substitutable functional groups may exist in the same group, not only one, but also a plurality, or plural types.

Examples of the aryl group having 6 to 30 carbon atoms include phenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, o-chlorophenyl, and m-chlorobenzene. P-chlorophenyl, o-fluorophenyl, p-mercaptophenyl, o-ethoxyphenyl, p-ethoxyphenyl, p-aminophenyl, p-cyanophenyl, α-naphthyl, β-naphthyl, o-biphenyl, m-biphenyl, p-biphenyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2- Fickey, 3-Ficky, 4-Ficky and 9-Ficky.

Further, as the oxyalkylene group, for example, oxyethyl group, oxypropyl group, and the like are used, and oxyethyl group is particularly preferably used.

Examples of the epoxy compound represented by the formula (1) are as follows.

M1 in the above formula (1-1) is an integer of 1 to 30.

M2 in the above formula (1-2) is an integer of 1 to 30, and may be, for example, 16.

M3 in the above formula (1-7) is an integer of 1 to 3.

M4 in the above formula (1-8) is an integer of 1 to 10.

M5 in the above formula (1-10) is an integer of 1 to 10, and may be set to 5, for example.

As described above, as the binder used in the present invention, in addition to the carboxyl group-containing polysaccharide, a reaction product obtained by reacting a carboxyl group-containing polysaccharide with an epoxy compound can be used.

The reaction product can be produced by dissolving the carboxyl group-containing polysaccharide and the epoxy compound in an aqueous medium, and reacting at a temperature of 80 to 120 ° C (for example, reflux temperature) for 12 to 48 hours.

The obtained reaction product is dissolved in an aqueous medium (for example, pure water) so as to have a concentration of 3% by mass, and the aqueous solution is measured at a constant temperature at a temperature of 25 ° C. to make the viscosity 20 to 1500 mPa‧s, or The above reaction product in the range of 10 to 2500 mPa · s is preferable.

The above-mentioned viscosity measurement can be performed using an E-type rotary viscometer, and can be measured using, for example, Toki Sangyo Co., Ltd. (TVE-22L, TVE-22H type).

Among the electrode active materials used in the present invention, examples of the positive electrode active material include lithium composite oxides and organic conductive polymers. Examples of the lithium composite oxide system include oxides of transition metals such as iron, cobalt, nickel, and manganese. Specifically, for example, Li _x CoO ₂ (0 <x ≦ 1.0), Li _x NiO ₂ (0 <x ≦ 1.0), Li _x Co _y Ni _1-y O ₂ (0 <x ≦ 1.0, 0 <y ≦ 1.0), Li _x MnO ₂ (0 <x ≦ 1.0), Li _x Mn ₂ O ₄ (0 <x ≦ 1.0), Li _x FeO ₂ (0 <x ≦ 1.0), Li _x FePO ₄ (0 <x ≦ 1.0), and the like. As the positive electrode active material made of an organic conductive polymer, for example, polyacetylene, poly-p-phenylene, or the like can be used.

Examples of the negative electrode active material in the electrode active material include carbon materials such as natural graphite or artificial graphite, amorphous carbon, conductive polymer compounds such as polyacene, and metal oxides such as tin oxide or silicon oxide. , Metal composite oxides, metal carbides that combine silicon with carbon, and lithium Or lithium alloys such as lithium aluminum alloys, and metals such as tin, zinc, and silicon that can form alloys with lithium.

Among them, as the electrode active material used in the present invention, lithium-cobalt composite oxide or graphite is preferred.

The electrode forming material system of the present invention may further include a conductive auxiliary agent.

As the conductive auxiliary agent used in the present invention, a carbon material such as carbon black, acetylene black, nano carbon fiber, or the like can be suitably used.

A method for producing an electrode using the electrode forming material is also an object of the present invention.

Specifically, it is a method of manufacturing an electrode including the following steps: a step of manufacturing a slurry of an electrode forming material by mixing an electrode forming material (electrode active material and preferably a conductive additive and a binder) with water; A step of applying the slurry of the electrode forming material on a current collector, heating the electrode forming material at a temperature of 80 to 160 ° C. to form a film of the electrode forming material; and pressing the aforementioned film from above the film.

The above slurry is obtained by adding an electrode active material, preferably a conductive auxiliary agent, and a binder to the water for stirring. In addition, it can also be obtained by adding an electrode active material and a conductive auxiliary agent to the binder aqueous solution in which the binder is dissolved in the water, and stirring it.

The ratio of the binder to water is preferably set such that the binder becomes an aqueous solution of 1 to 10% by mass, and particularly preferably set to the aqueous solution of about 3% by mass of the binder.

The water used for preparing the electrode-forming material slurry is preferably pure water.

The electrode active material can be set within a range of 80 to 98% by mass with respect to the total mass of the constituent components (electrode active material + conductive aid + binder) of the electrode forming material.

In addition, the conductive additive may be set within a range of 0 to 10% by mass based on the total mass of the constituent components (electrode active material + conductive additive + binder) of the electrode forming material.

In addition, the binder may be set within a range of 2 to 20% by mass with respect to the total mass of the constituent components (electrode active material + conductive aid + binder) of the electrode forming material.

The slurry of the electrode forming material obtained in this way is preferably one having a solid content concentration of 20 to 70% by mass and a viscosity in the range of 500 to 3,000 mPa · s.

As the current collecting system, a known one can be used. For example, the current collector used as the positive electrode is aluminum, stainless steel, or the like, and the current collector used as the negative electrode is copper, nickel, or the like, and a plate-shaped foil can be used.

There is no particular limitation on the method of coating the current collector with the slurry of the electrode-forming material produced in this manner. Various types of coaters such as a roll coater, a knife coater, and the like can be used to coat the surface of the current collector.

The electrode forming material coated on the surface of the current collector is dried at 80 to 160 ° C and used as a coating for the electrode forming material. Then, the coating is pressed to increase the density of the electrode active material to form an electrode. pressing It is carried out using general-purpose pressing such as heating roll pressing, cold pressing roll pressing, and flat plate pressing.

The thickness of the layer of electrode forming material (pressed film) formed on the surface of the current collector can be set to a film thickness of 40 to 100 μm.

[Example] [Synthesis Example 1] Synthesis of Polymer 1

In a 500 mL separatory bottle, ultrapure water (392 g) and carboxymethyl cellulose-ammonium salt (8 g) were added, and they were uniformly dissolved after stirring with a mechanical stirrer at 300 rpm. This solution was charged with polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether with a weight average molecular weight Mw of 500, and the number of repeating units n of oxyethylene was 8 ~ 9, equivalent to formula (1-1)) (12.1 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (1.5 L), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 8.5 g of polymer 1. The obtained compound was dissolved in ultrapure water and adjusted to a viscosity of 226 mPa · s when it became a 3% by mass aqueous solution. (Measured at 10 rpm).

[Synthesis Example 2] Synthesis of Polymer 2

In a 500 mL separation bottle, ultrapure water (196 g) and carboxymethyl cellulose-ammonium salt (4 g) were added, and they were uniformly dissolved by stirring at 300 rpm with a mechanical stirrer. This solution was charged with polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether with a weight average molecular weight Mw of 500, and the number of repeating units n of oxyethylene was 8 ~ 9, equivalent to formula (1-1)) (3.1 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (1.0 L), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 4.2 g of polymer 2. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 1086 mPa · s (using an E-type rotary viscosity meter (TVE-22H type) manufactured by Toki Sangyo Co., Ltd. at 25 ° (Measured at 10 rpm).

[Synthesis Example 3] Synthesis of Polymer 3

In a 500 mL separatory bottle, ultrapure water (245 g) and carboxymethyl cellulose-ammonium salt (5 g) were added, and they were uniformly dissolved by stirring at 300 rpm with a mechanical stirrer. This solution was charged with the trade name Denacol EX-171 (manufactured by Nagase Chemtex) and the composition was Lauryl Alcohol (EO) 15 Glycidyl Ether, which was equivalent to formula (1-2) (m2 = 16)) (3.0 g), Stir by refluxing for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (1.5 LmL), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 4.0 g of polymer 3. Dissolve the obtained polymer The viscosity when dissolved in ultrapure water and adjusted to a 3% by mass aqueous solution was 1163 mPa · s (measured at 25 ° C and 10 rpm by an E-type rotary viscometer (TVE-22H) manufactured by Toki Sangyo Co., Ltd.) .

[Synthesis Example 4] Synthesis of Polymer 4

In a 500 mL separation bottle, ultrapure water (196 g) and carboxymethyl cellulose-ammonium salt (4 g) were added, and they were uniformly dissolved by stirring at 300 rpm with a mechanical stirrer. This solution was charged with the brand name Denacol EX-314 (manufactured by Nagase Chemtex, and the composition was Glycerol Polyglycidyl Ether, which was equivalent to formula (1-3) and formula (1-4)) (4.0 g), and was refluxed Stir for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (1.0 L), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 4.2 g of polymer 4. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 140 mPa · s (using an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 ° C Measurement at 10 rpm).

[Synthesis Example 5] Synthesis of Polymer 5

In a 500 mL separatory bottle, ultrapure water (98 g) and carboxymethyl cellulose-ammonium salt (2 g) were added, and they were uniformly dissolved by stirring at 300 rpm with a mechanical stirrer. Polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether, oxygen, The number of repeating units n of the ethylenic group is 8 to 9, which corresponds to formula (1-1)) (4.7 g), and is stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered by suction filtration, and then dried under reduced pressure at 50 ° C to recover 2.2 g of polymer 5. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 1179 mPa · s (using an E-type rotary viscometer (TVE-22H type) manufactured by Toki Sangyo Co., Ltd. at 25 ° C (Measured at 10 rpm).

[Synthesis Example 6] Synthesis of Polymer 6

In a 500 mL separatory bottle, add ultrapure water (98 g) and carboxymethyl cellulose-sodium salt (2 g: viscosity in 3% aqueous solution = 3688 cP), and stir with a mechanical stirrer at 300 rpm to make it uniform. Dissolve. This solution was charged with polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether with a weight average molecular weight Mw of 500, and the number of repeating units n of oxyethylene was 8 ~ 9, equivalent to formula (1-1)) (3.1 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered by suction filtration, followed by drying under reduced pressure at 50 ° C to recover 2.3 g of polymer 6. The obtained polymer was dissolved in ultrapure water, and its viscosity when adjusted to a 3% by mass aqueous solution was 333 mPa · s (using an E-type rotary viscometer (TVE-22L type manufactured by Toki Sangyo) at 25 ° C Measurement at 10 rpm).

[Synthesis Example 7] Synthesis of Polymer 7

In a 500 mL separatory bottle, ultrapure water (98 g) and sodium alginate (2 g) were added and stirred at 300 rpm with a mechanical stirrer to uniformly dissolve them. This solution was charged with polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether with a weight average molecular weight Mw of 500, and the number of repeating units n of oxyethylene was 8 ~ 9, equivalent to formula (1-1)) (1.0 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered by suction filtration, followed by drying at 50 ° C under reduced pressure to recover 1.8 g of polymer 7. The obtained polymer was dissolved in ultrapure water and adjusted to a viscosity of 62 mPa · s when it became a 3% by mass aqueous solution (using an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 ° C Measurement at 10 rpm).

[Synthesis Example 8] Synthesis of Polymer 8

In a 500 mL separatory bottle, add ultrapure water (98g) and carboxymethyl cellulose-sodium salt (the viscosity in a 3% by mass aqueous solution is determined by a Toki Sangyo Co., Ltd. E-type rotary viscometer (TVE -22H type) was measured at 25 ° C and 10 rpm as 6500 mPa · s) (2 g), and was stirred at 300 rpm with a mechanical stirrer to be uniformly dissolved. This solution was charged with the brand name Denacol EX-171 (manufactured by Nagase Chemtex) and the composition was Lauryl Alcohol (EO) 15 Glycidyl Ether, which is equivalent to the formula (1-2) (m2 = 16)) (2.0 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered by suction filtration, and then dried under reduced pressure at 50 ° C to recover 2.1 g of polymer 8. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 21.5 mPa · s (using an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 (Measured at 10 rpm at 10 ° C).

[Synthesis Example 9] Synthesis of Polymer 9

In a 500 mL separatory bottle, ultrapure water (98 g) and sodium alginate (2 g) were added and stirred at 300 rpm with a mechanical stirrer to uniformly dissolve them. This solution was charged with polyethylene glycol diglycidyl ether (manufactured by SIGMA-ALDRICH, trade name Poly (ethylene glycol) diglycidyl ether with a weight average molecular weight Mw of 500, and the number of repeating units n of oxyethylene was 8 ~ 9, equivalent to formula (1-1)) (4.0 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 1.9 g of polymer 9. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 5.5 mPa · s (with an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 (Measured at 10 rpm at 10 ° C).

[Synthesis Example 10] Synthesis of Polymer 10

In a 500 mL separatory bottle, add ultrapure water (196 g) and carboxymethyl cellulose-sodium salt (the viscosity in a 3% by mass aqueous solution is determined by a Toki Sangyo Co., Ltd. E-type rotary viscometer (TVE -22H type) was measured at 25 ° C and 10 rpm as 6500 mPa · s) (4 g), and was stirred at 300 rpm with a mechanical stirrer to be uniformly dissolved. Denacol EX-171 (manufactured by Nagase Chemtex) was charged with Lauryl Alcohol (EO) 15 Glycidyl Ether (equivalent to formula (1-2) (m2 = 16)) (4 g), and stirred under reflux for 24 hours. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (1000 mL), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C to recover 3.5 g of polymer 10. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 15 mPa · s (using an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 ° C Measurement at 10 rpm).

[Synthesis Example 11] Synthesis of Polymer 11

In a 500 mL separatory bottle, add ultrapure water (97 g) and carboxymethyl cellulose-sodium salt (the viscosity in a 3% by mass aqueous solution is determined by a Toki Sangyo Co., Ltd. E-type rotary viscometer (TVE -22H type) was measured at 25 ° C and 10 rpm = 3688 mPa · s) (3g), and the mixture was uniformly dissolved after being stirred at 300 rpm with a mechanical stirrer. Filled with Denacol EX-171 (made by Nagase Chemtex, the composition is Lauryl Alcohol (EO) 15 Glycidyl Ether, which is equivalent to formula (1-2) (m2 = 16)) (6g), stirred for 24 hours under reflux. After completion of the reaction, the temperature of the reaction solution was lowered to room temperature. This reaction solution was dropped into acetone (500 mL), and the precipitate was recovered through suction filtration, and then dried under reduced pressure at 50 ° C. to recover 2.9 g of polymer 11. The obtained polymer was dissolved in ultrapure water, and the viscosity when adjusted to a 3% by mass aqueous solution was 11 mPa · s (using an E-type rotary viscometer (TVE-22L type) manufactured by Toki Sangyo Co., Ltd. at 25 ° C Measurement at 10 rpm).

[Example 1] (Manufacturing of negative electrode)

Polymer 1 was added to 95 parts by mass of graphite as a negative electrode active material and trade name KS-4 (registered trademark of Timcal Graphite and Carbon, a component containing carbon) as a conductive additive, to 2 parts by weight of polymer 1 so that 3 parts by mass of water was added and mixed thoroughly to obtain a slurry for a negative electrode (the solid content of the slurry was 51% by mass, and the viscosity of the slurry was 1560 mPa · s). This negative electrode slurry was coated on a copper foil having a thickness of 20 μm, dried, and then pressed to obtain a negative electrode. The thickness of the electrode-forming material layer was 80 μm.

The mass of the obtained negative electrode was measured, and the electrode density was calculated by dividing the mass by the volume calculated from the thickness and area of the negative electrode.

(Confirmation of coating property on current collector)

The previously obtained electrodes were subjected to visual and electron microscopy ((share) (Hitachi High-Technologies, S-4800) was observed to confirm whether any part of the current collector was exposed in the electrode.

In addition, it was visually confirmed whether the copper foil of the current collector was visible from the upper part of the electrode, and the presence or absence of peeling of the electrode was confirmed.

(Manufacturing of batteries)

After the negative electrode obtained previously was cut into a 15.5 mm diameter circle, a lithium metal foil was used as a counter electrode in a 2032 type coin cell stainless steel coin outer container, and a separator (Celgard) was sandwiched between the electrodes. A few drops of an electrolytic solution were dropped on the solution, and the electrolytic solution was dissolved in a mixed solution of 1: 1/1: 1 (volume ratio) of ethyl carbonate / ethyl methyl carbonate / diethyl carbonate at a concentration of 1 mol / L. There was LiPF ₆ as an electrolyte and 2 parts by mass of vinylene carbonate was added. Thereafter, a cap made of stainless steel was covered with a sealing gasket made of polypropylene and sealed with an inserting tool for coin cell production, and then a battery for negative electrode evaluation was produced.

(Evaluation of battery performance)

This battery was charged and discharged from 0.05V to 3.0V through a constant current equivalent to 0.05C. The initial irreversible capacity at this time was 21 mAh / g. After that, the discharge capacity during charging and discharging from 0.05V to 3.0V at a constant current equivalent to 0.2C was 2.46mAh.

[Examples 2 to 4]

Instead of polymer 1, in addition to using polymers 2 to 4, In the same manner as in Example 1, the production of the negative electrode, the confirmation of the applicability on the current collector (the presence or absence of the current collector), the confirmation of the presence or absence of electrode peeling, battery production, and evaluation of battery performance were performed. A case where the polymer 2 is used is Example 2, a case where the polymer 3 is used is Example 3, and a case where the polymer 4 is used is Example 4.

[Examples 5 to 8]

Instead of polymer 1, except that polymers 5 to 8 were used, the negative electrode was manufactured by the same method as in Example 1, and the applicability of the current collector was confirmed (the presence or absence of the current collector). Whether the electrode is peeled off. Example 5 is the case where polymer 5 is used, Example 6 is the case where polymer 6 is used, Example 7 is the case where polymer 7 is used, and Example 8 is the case where polymer 8 is used.

[Example 9] (Manufacture of positive electrode)

Polymer 1 was added to lithium mass acid as a positive electrode active material at 90 parts by mass and trade name Super-P (registered trademark of Timcal Graphite and Carbon Co., Ltd., a component containing carbon) as a conductive additive, in 5 parts by mass. After adding 5 parts by mass and adding water, the slurry for the positive electrode was obtained by mixing thoroughly (the solid content of the slurry was 40% by mass, and the viscosity of the slurry was 2640 mPa · s). This positive electrode slurry was coated on an aluminum foil having a thickness of 20 μm and dried to obtain a positive electrode. The thickness of the electrode-forming material layer was 50 μm. Still, determine the mass of the obtained positive electrode, and This mass is divided by the volume calculated from the thickness and area of the positive electrode to calculate the electrode density.

The above-mentioned positive electrode was confirmed in the same manner as in Example 1 for the applicability on the current collector (the presence or absence of the current collector exposure) and the presence or absence of electrode peeling.

[Example 10]

Instead of polymer 1, except that the carboxymethyl cellulose-sodium salt whose viscosity in a 3% by mass aqueous solution was measured at 25 ° C at 10 rpm was 280 mPa · s, by the same method as in Example 1, Manufacture of a negative electrode, confirmation of coating properties on a current collector (presence or absence of current collector exposure), confirmation of presence or absence of electrode peeling, battery manufacturing, and evaluation of battery performance.

[Examples 11 to 12]

Instead of polymer 1, in addition to using a polymer having a viscosity of 238 mPa‧s in a 3% aqueous solution prepared by mixing polymer 10 with a carboxymethyl cellulose-sodium salt having a viscosity of 6500 mPa‧s in a weight ratio of 10: 3 (Example 11) or a polymer having a viscosity of 206 mPa · s by mixing a polymer 11 with a carboxymethyl cellulose-sodium salt having a viscosity of 3688 mPa · s and mixing the polymer 11 at a weight ratio of 10: 4 Except for Example 12, the same method as in Example 1 was used to manufacture the negative electrode, confirm the applicability on the current collector (presence or absence of current collector exposure), and confirm the presence or absence of electrode peeling.

[Comparative Example 1]

Instead of polymer 1, the viscosity of a carboxylic acid used in a 3% by mass aqueous solution (measured at 25 ° C and 10 rpm by an E-type rotary viscometer (TVE-22H type) manufactured by Toki Sangyo Co., Ltd.) was 4282 mPa · s. Except for the methyl cellulose-ammonium salt, the same method as in Example 1 was used to manufacture the negative electrode, confirm the coating property on the current collector (the presence or absence of the current collector exposure), and confirm the presence or absence of electrode peeling. , Battery manufacturing, battery performance evaluation.

[Comparative Examples 2 to 3]

Instead of polymer 1, except that the viscosity used in a 3% by mass aqueous solution (measured with an E-type rotary viscometer (TVE-22H type manufactured by Toki Sangyo Co., Ltd. at 25 ° C and 10 rpm)) was 6500 mPa‧s Except for carboxymethyl cellulose-sodium salt (Comparative Example 2) and carboxymethyl cellulose-sodium salt (Comparative Example 3) of 2807 mPa · s, the same method as in Example 1 was used to produce a negative electrode. Confirmation of coating properties on the electrical body (presence or absence of current collector exposure) or presence or absence of electrode peeling.

[Comparative Example 4]

Instead of polymer 1, except for a viscosity of 3% by mass in an aqueous solution (measured at 25 ° C and 10 rpm by an E-type rotary viscometer (TVE-22H) manufactured by Toki Sangyo Co., Ltd.) of 1643 mPa Except for sodium, the same method as in Example 1 was used to manufacture the negative electrode, Confirmation of the applicability on the current collector (presence or absence of current collector exposure), or presence or absence of electrode peeling.

[Comparative Example 5]

Instead of the polymer 1, except that the polymer 9 was used, the same method as in Example 1 was used to carry out the production of the negative electrode, the confirmation of the coating property on the current collector (the presence or absence of the current collector), and the peeling of the electrode. Confirmation.

[Comparative Example 6]

Instead of polymer 1, the viscosity of a carboxylic acid used in a 3% by mass aqueous solution (measured at 25 ° C and 10 rpm by an E-type rotary viscometer (TVE-22H type) manufactured by Toki Sangyo Co., Ltd.) was 4282 mPa · s. Except for the methyl cellulose-ammonium salt, the same method as in Example 8 was used to manufacture the negative electrode, confirm the applicability on the current collector (the presence or absence of the current collector), and confirm the presence or absence of electrode peeling. .

The results of the above examples and comparative examples are summarized in Tables 1 and 2 below.

Regarding the presence or absence of the current collector, the electron microscope photographs are shown in FIGS. 1 to 15 and 17 to 19 (the photographs show that the left half is 500 times at a magnification, and the right half is 1000 times at a magnification. Photographed portion), and photographs of the electrodes of Example 1 and Comparative Example 5 for confirming the presence or absence of electrode peeling are shown in FIG. 16. As shown in FIG. 16, in Comparative Example 5, it was confirmed that the portion where the copper foil was visible on the outer peripheral portion of the electrode (peeling section).

As shown in Tables 1 and 2, the lithium ion battery (Examples 1 to 12) using the electrode produced by the electrode forming material of the present invention maintains or improves the characteristics during charge and discharge, and compares with the comparative example. (1 to 6) results in that the coating property to the current collector is excellent.

[Industrial availability]

The present invention relates to the activity of an electrode coated with a current collector when an electrode active material and a conductive auxiliary agent are coated with a binder through an adhesive. The substance is a high-density binder with excellent adhesion to a current collector, and can produce an electrode-forming material including the binder, and form an electrode using the electrode-forming material and a high-performance battery.

Claims (7)

An electrode forming material is an electrode forming material coated on a current collector. The electrode forming material includes an electrode active material and a binder. The binder includes a reaction product of a carboxyl group-containing polysaccharide and an epoxy compound. In addition, the 3% by mass aqueous solution of the adhesive has a viscosity in the range of 20 to 1500 mPa‧s at 25 ° C. The electrode forming material according to claim 1, wherein the carboxyl group-containing polysaccharide is at least one selected from the group consisting of carboxymethyl cellulose, alginic acid, and salts thereof. The electrode forming material according to claim 1 or claim 2, wherein the aforementioned epoxy compound is an epoxy compound represented by formula (1):

(In formula (1), X represents a hydrogen atom, a mono- or poly (oxyalkylene) group having 1 to 30 repeat units, an n-valent aliphatic hydrocarbon group having 1 to 30 carbon atoms that can be substituted, (Aryl groups having 6 to 30 carbon atoms, or a combination thereof, n is an integer of 1 to 10). The electrode forming material according to claim 1 or claim 2, which further contains a conductive auxiliary agent. The electrode forming material according to claim 1 or claim 2, wherein the electrode active material is lithium cobalt composite oxide or graphite. The electrode forming material according to claim 4, wherein the aforementioned conductive auxiliary agent is made of carbon material. A method for manufacturing an electrode, comprising the steps of: mixing the electrode-forming material of any one of claim 1 to claim 6 with water to produce a slurry of the electrode-forming material; mixing the slurry of the electrode-forming material The step of applying the material to the current collector, heating at a temperature of 80 to 160 ° C and forming the coating of the electrode forming material; the step of pressing the foregoing coating from above the coating.